1. Field of the Invention
This invention relates to an apparatus for displaying an image of a wide field angle, and particularly to an image display apparatus adapted to be mounted on the head portion or face of a person who observes an image and enable the person to observe the image information of a small display element such as a liquid crystal display element or a CRT therethrough while enlarging the image information as a virtual image.
2. Related Background Art
A display apparatus using a multilayer film reflecting surface or an optically transparent beam coupling element such as a hologram optical element to enable display information (image information) from a display element and image information such as a scene in the external world to be spatially superposed one upon the other in the same field of view and observed is generally called a head up display apparatus and is utilized in various fields. Also, a display apparatus in which the beam combiner is provided at a location relatively near to an observer""s eyes in order to make the parts of the optical device of the head up display apparatus small and the optical device is mounted on a helmet is called a helmet mounted display apparatus (HMD apparatus), and its various applications to a display apparatus for the operation of an aircraft, a display apparatus for amusements such as games or for virtual reality, etc. have been proposed.
FIG. 1 of the accompanying drawings is a schematic view of an HMD apparatus as a display apparatus described in U.S. Pat. No. 4,028,725. Display lights emitted from CRTs 101 and 102 are made into substantially parallel beams of light by collimator lenses 103 and 108 and are reflected by mirrors 104 and 107, respectively, and the display lights from the two CRTs 101 and 102 are superposed one upon the other by dichroic mirrors 105 and 109. The display lights thus superposed one upon the other have their direction again changed by a mirror 106 and are enlarged through a lens 110, and are directed to an observer""s pupil 114 by a half mirror 111. At this time, the CRT 101 displays a wide field image 113 and the CRT 102 displays a narrow field image 112. Also, the dichroic mirror 109 is installed so as to shield the vicinity of the center of the dichroic mirror 105 from light and therefore, the observer can observe the wide field image 113 displayed by the CRT 101 and the narrow field image 112 from the CRT 102 displayed near the center thereof while superposing these images upon a scene or the like behind the half mirror 111.
Also, in this example of the prior art, a so-called purkinje image provided by the light from a light source 115 of infrared rays being reflected by the observer""s pupil 114 is detected by a detection unit 119 comprising a beam splitter 116 and photodiodes 117, 118, whereby the observer""s visual axis direction is detected.
The output of this visual axis detecting means is inputted to the servo system (not shown) of the movable half mirror 111 and thus, the aforementioned two field images are always displayed forwardly in the observer""s visual axis direction.
In the example of the conventional art shown in FIG. 1, the field angles of the wide field image and the narrow field image are 25xc2x0 and 5xc2x0, respectively, and the narrow field image is displayed with a high resolution, whereby with the displayed image of the high resolution as the center of the field of view, the wide field image is always observed around it. In the above-described example of the conventional art, however, design is made such that the image formed by the wide field image and the narrow field image being superposed one upon the other is always presented at the central portion of the field of view by the half mirror 111 controlled by the signal from the visual axis detecting means, and this has led to a problem that even if the observer gazes at any point on the wide field image, the image is not visually recognized at the center of the field of view and the portion intended by the observer cannot be observed. Also, a field angle much wider than the field angle as in the above-described example of the prior art, e.g. 25xc2x0, is required of the display apparatus for virtual reality and for example, a display for displaying a field angle of 88xc2x0 by one eye has been commercialized, but in these apparatuses, the resolution of the displayed image depends on the pixel density of the liquid crystal display element used, and this has led to a disadvantage that at present, the displayed image does not have a sufficient resolution.
It is the object of the present invention to provide an image display apparatus for enabling an observer to observe the image of a place the observer wants to seen in a wide field image by a highly fine image, and an image photographing apparatus therefor.
To achieve the above object, one form of the image display apparatus of the present invention is characterized by first image generating means for displaying first image information by a plurality of pixels emitting light, second image generating means for displaying second image information by a plurality of pixels emitting light, the second image information being part of the first image information, visual axis detecting means for detecting an observer""s visual axis direction optical means for combining a first image from the first image generating means and a second image from the second image generating means, moving the second image relative to the first image in conformity with an output signal from the visual axis detecting means and turning it to the observer""s pupil, the marginal portion of the second image being made substantially coincident with the boundary between the pixels of said first image when the images are combined and image display changing means for changing said first image information and the second image information on the basis of the output signal of the visual axis detecting means.
In a further preferred form, the size of the second image is integer times as great as the interval between the pixels (or the size of the pixel) of the first image when the images are combined.
In still a further preferred form, the first image information in an area wherein the first image and the second image are superposed one upon the other when the images are combined is the second image information.
In yet still a further preferred form, the area of the images superposed one upon the other is not displayed by the first image generating means.
In a further preferred form, the pixel density in the central portion of the second image is higher than the pixel density of the first image and the pixel density in the marginal portion of the second image is substantially the same as the pixel density of the first image when said images are combined.
In still a further preferred form, the luminance in the central portion of the second image is higher than the luminance of the first image and the luminance in the marginal portion of the second image is substantially the same as the luminance of the first image when the images are combined.
In yet still a further form, the first and second images are combined on an intermediate imaging plane through respective relay lenses, are enlarged as virtual images and are turned to the observer""s pupil.
In a further preferred form, the relay lenses have different imaging magnifications.
Another form of the image display apparatus of the present invention is characterized in that the image display apparatus is provided correspondingly to each of the observer""s left and right eyes.
In a further preferred form, the second image generating means corresponding to the left and right eyes display parallax image information corresponding to the respective eyes.
In still a further preferred form, the first image generating means is used in common.
Another form of the image display apparatus of the present invention is characterized by first image generating means for emitting light and displaying first image information second image generating means for emitting light and displaying second image information, the second image information being part of said first image information visual axis detecting means for detecting an observer""s visual axis direction head portion position detecting means for detecting the position of the observer""s head portion optical means for combining a first image from the first image generating means and a second image from the second image generating means, moving the second image relative to the first image in conformity with an output signal from the visual axis detecting means and turning it to the observer""s pupil and image information changing means for changing the first image information and the second image information on the basis of the output signal of the visual axis detecting means and the output signal of the head portion position detecting means.
A further preferred form has an image memory having recorded therein the image all around a predetermined position, and inputs a part of said image memory to said first image generating means as the first image information in conformity with the output signal of the head portion position detecting means.
One form of the image photographing apparatus of the present invention is an image photographing apparatus for an image display apparatus for displaying, on the basis of output signals from visual axis detecting means for detecting the visual axis direction of an observer who observes a first image from first image generating means for displaying first image information and head portion position detecting means for detecting the position of the observer""s head portion, a combined image of said first image and a second image from second image generating means for displaying second image information which is part of the first image information, characterized by first image pickup means for obtaining the first image information second image pickup means for obtaining the second image information means for controlling the photo-taking direction of the first image pickup means in conformity with the output signal from the head portion position detecting means and means for controlling the photo-taking direction of the second image pickup means in conformity with the output signal from the visual axis detecting means.
A further preferred form has means for transmitting the image information obtained from the first image pickup means to the image display apparatus while making the compression rate of the image information higher than that of the image information obtained from said second image pickup means.
In still a further preferred form, the image photographing apparatus is provided correspondingly to each of the observer""s left and right eyes.
In yet still a further preferred form, said first image pickup means is used in common.
Some specific embodiments of the image display apparatus of the present invention will become apparent from the following detailed description thereof.